Mg-Zn Oxide Tunnel Barriers and Method of Formation

• US 20080138660A1
• Filed: 07/12/2007
• Published: 06/12/2008
• Est. Priority Date: 12/12/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Parkin, Stuart Stephen Papworth
• Granted Patent: US 7,606,010 B2
• Time in Patent Office: Days
• US Class Current: 428/812
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3268 the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
• CPC Class Codes: H01F 10/3281 only by use of asymmetry of the magnetic film pair itself, i.e. so-called pseudospin valve [PSV] structure, e.g. NiFe/Cu/Co
• CPC Class Codes: H01F 10/329 Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect
• CPC Class Codes: H01F 10/3295 Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1143 with defined structural feature
• CPC Class Codes: Y10T 428/115 Magnetic layer composition
• CPC Class Codes: Y10T 428/1157 Substrate composition

Abstract

ZnMg oxide tunnel barriers are grown which, when sandwiched between ferri- or ferromagnetic layers, form magnetic tunnel junctions exhibiting high tunneling magnetoresistance (TMR). The TMR may be increased by annealing the magnetic tunnel junctions. The zinc-magnesium oxide tunnel barriers may be incorporated into a variety of other devices, such as magnetic tunneling transistors and spin injector devices. The ZnMg oxide tunnel barriers are grown by first depositing a zinc and/or magnesium layer onto an underlying substrate in oxygen-poor (or oxygen-free) conditions, and subsequently depositing zinc and/or magnesium onto this layer in the presence of reactive oxygen.

Claims

1. A structure, comprising:

a first magnetic layer including at least one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;

a magnesium-zinc oxide tunnel barrier; and

a second magnetic layer including at least one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials, wherein the first magnetic layer, the tunnel barrier, and the second magnetic layer form a magnetic tunnel junction in which;

i) the amount of any deleterious oxide in the magnetic tunnel junction is sufficiently low; and

ii) the magnetic tunnel junction is sufficiently free of defects, that the tunnel magnetoresistance of the magnetic tunnel junction is greater than 50% at room temperature.

2. The structure of claim 1, wherein at least one of the first magnetic layer and the second magnetic layer includes a spacer layer that is in contact with the tunnel barrier.

3. The structure of claim 1, wherein the tunnel barrier has a thickness of between 3 and 50 angstroms.

4. The structure of claim 1, in which:

i) the amount of any deleterious oxide in the magnetic tunnel junction is sufficiently low; and

ii) the magnetic tunnel junction is sufficiently free of defects, that the tunnel magnetoresistance of the magnetic tunnel junction is greater than 70% at room temperature.

5. The structure of claim 1, wherein at least one of the first magnetic layer and the second magnetic layer includes antiferromagnetic material that is exchange biased with ferromagnetic material of said at least one layer, the antiferromagnetic material including at least one alloy selected from the group consisting of Ir—

Mn and Pt—

Mn, in which the alloy is substantially (100) oriented and is at least substantially fcc.

6. The structure of claim 1, wherein the first magnetic layer includes antiferromagnetic material over at least one layer selected from the group consisting of Ta and TaN.

7. The structure of claim 1, wherein the tunnel barrier is in direct contact with both ferromagnetic material of the first magnetic layer and ferromagnetic material of the second magnetic layer.

8. The structure of claim 1, wherein each of the magnetic layers is ferromagnetic, bcc, and substantially (100) oriented.

9. The structure of claim 1, wherein the first magnetic layer and the second magnetic layer each include ferromagnetic material selected from the group consisting of i) Fe, ii) an alloy of Co and Fe, iii) an alloy of Ni and Fe, and iv) an alloy of Ni and Fe and Co.

10. The structure of claim 1, wherein the tunnel junction has been annealed at a temperature of at least 180°

C. to improve its tunnel magnetoresistance.

11. The structure of claim 1, wherein the tunnel junction has been annealed at a temperature of at least 220°

C. to improve its tunnel magnetoresistance.

12. The structure of claim 1, wherein the tunnel junction has been annealed at a temperature of at least 360°

C. to improve its tunnel magnetoresistance.

13. The structure of claim 1, wherein the tunnel barrier is substantially (100) oriented.

14. The structure of claim 1, wherein the tunnel barrier has the cubic rock salt structure.

15. The structure of claim 1, comprising a tunnel barrier in which the atomic concentration of Zn is greater than the atomic concentration of Mg.

16. A structure, comprising:

a first ferromagnetic layer that is bcc and substantially (100) oriented;

a magnesium-zinc oxide tunnel barrier that is substantially (100) oriented; and

a second ferromagnetic layer that is bcc and substantially (100) oriented, wherein the first ferromagnetic layer, the tunnel barrier, and the second ferromagnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance greater than 50% at room temperature.

17. A structure, comprising:

a first magnetic layer;

a magnesium-zinc oxide tunnel barrier; and

a second magnetic layer, wherein the first magnetic layer, the tunnel barrier, and the second magnetic layer are in proximity with each other and form a magnetic tunnel junction, thereby permitting spin-polarized current to pass through the structure, and in which;

i) the amount of any deleterious oxide in the magnetic tunnel junction is sufficiently low; and

ii) the magnetic tunnel junction is sufficiently free of defects,

that the tunnel magnetoresistance of the magnetic tunnel junction is greater than 100% at room temperature.

18. The structure of claim 17, wherein each of the magnetic layers is ferromagnetic, bcc, and substantially (100) oriented.

19. The structure of claim 18, wherein the tunnel barrier is substantially (100) oriented.

20. The structure of claim 19, wherein the tunnel junction has been annealed at a temperature of at least 220°

C. to improve its tunnel magnetoresistance.